Method of determining coordinate on micro dotmap according to moving vector

ABSTRACT

When a user holds an optical scanning device to scan a micro dotmap on a displaying medium, a coordinate of a frame center of a retrieved frame on the displaying medium is calculated according to a decoding method for the micro dotmap in advance. A moving vector corresponding to a difference between difference frames scanned by the optical scanning device at different moments is calculated so that an instant location of the frame center on the displaying medium can be calculated anytime. Therefore, a large number of calculations brought by frequent decoding may be saved since merely a few calculations are required in calculating the moving vector. By further decoding the coordinate of the frame center at moments spaced with constant or variable intervals, errors brought by vibrations of the displaying medium are instantly fixed. Accumulated errors are avoided in the calculated instant locations of the frame center anytime.

CROSS REFERENCE TO RELATED APPLICATIONS

This continuation application claims priority of U.S. Pat. No. 8,513,546B2 filed on Dec. 22, 2008.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The claimed invention discloses a method of determining a coordinate ona micro dotmap, and more particularly, to a method of determining acoordinate on a micro dotmap according to a moving vector.

2. Description of the Prior Art

Please refer to FIG. 1, which illustrates scanning a displaying mediumprinted with a micro dotmap by manipulating an optical scanning devicein a hand-writing manner so as to display tracks of the optical scanningdevice on a screen corresponding to a movement of the optical scanningdevice on the displaying medium. And please refer to FIG. 2, whichillustrates a frame retrieved by scanning the displaying medium shown inFIG. 1 with the optical scanning device shown in FIG. 1. As shown inFIG. 1, a displaying medium 104 is printed with a micro dotmap, wheremicrodots printed on the micro dotmap are printed with a particularencoding method. When a user holds an optical scanning device 106 toscan the micro dotmap printed on the displaying medium 104, a frame 120scanned by the optical scanning device 106 on the displaying medium 104is transmitted to a screen 102 so as to display a location, which is ofthe held optical scanning device 106 on the displaying medium 104, onthe screen 102. As shown in FIG. 2, the frame 120 scanned in FIG. 1covers a plurality of encoding blocks 122. Each encoding block 122 isprinted with a plurality of microdots 128 having differentcharacteristics, and is separated into a header region 124 and a dataregion 126. The header region 124 is used for having an encoding block122 having said header region 124 be recognizable, therefore, as shownin FIG. 2, a combination or a permutation of the plurality of microdots128 comprised by the header region 124 of each encoding block 122 is thesame. The plurality of microdots 128 comprised by each data region 126are encoded with a particular encoding method so as to indicate acoordinate of an encoding block 122 having said data region 126 on thedisplaying medium 104, where the encoding method is substantiallyimplemented on the combination or the permutation of the plurality ofmicrodots 128 of each data region 126. As shown in FIG. 2, each encodingblock 122 exclusively occupies one particular among the coordinates (x,y), (x+1,y), (x, y+1), and (x+1, y+1), each of which may be retrieved byperforming a decoding procedure corresponding to the abovementionedencoding method on the plurality of microdots 128 of the data region 126of each encoding block 122. When the optical scanning device 106 scansthe frame 120, a domain of each scanned encoding block 122 is firstrecognized according to a data region 124 of each the scanned encodingblock 122, then a plurality of microdots 128 in a data region 126 ofeach the scanned encoding block 122 are decoded so as to determine acoordinate of each the scanned encoding block 122 on the displayingmedium 104.

Methods mentioned in FIG. 1 and FIG. 2 are primarily applied on devicessuch as a Braille plate. A user may hold the optical scanning device 106to scan and move on the displaying medium 104 so as to correspondinglyoperate on the screen 102, or to have the screen 102 to serve as awhiteboard by directly displaying movements of the held optical scanningdevice 106 on the screen 102. The displaying medium 104 is a paperprinted with a micro dotmap or a printable medium capable of beingprinted with the micro dotmap. The optical scanning device 106 may alsobe a conventional scanning device capable of recognizing microdots onthe micro dotmap. When the user holds the optical scanning device 106,the scanned frame 120 is directly transmitted to the screen 102 having aprocessing unit. After the processing unit performs the abovementionedrecognition and decoding procedure on the frame 120, a current locationof the optical scanning device 106 on the displaying medium 104 is alsodisplayed on the frame 120 displayed by the screen 102. After a shortwhile, when the user holds the optical scanning device 106 to move andscan on the displaying medium 104, another frame 120 is fetched and isalso processed by the processing unit of the screen 102 to be recognizedand decoded.

However, in the abovementioned decoding procedure, a coordinate of eachencoding block 122 covered by the frame 120 is retrieved by directlydecoding the plurality of microdots 128 of the data region 126; if theuser holds the optical scanning device 106 to rapidly move and scan onthe displaying medium 104, a significant amount of calculations arebrought since the plurality of microdots 128 of the data region 126 haveto be instantly recognized and decoded. The significant amount ofcalculations lead to severe delays on the screen 102 in displaying themovements of the held optical scanning device 106, and bring significantinconveniences to the user.

SUMMARY OF THE INVENTION

The claimed invention discloses a method of determining a coordinate ona micro dotmap according to a moving vector. The method comprisesdecoding a first coordinate of a first frame corresponding to a firstdisplaying medium according to the first frame retrieved by scanning thefirst displaying medium at a first moment; calculating a first movingvector according to both the first frame and a second frame at a secondmoment; and determining a second coordinate of the second framecorresponding to the first displaying medium according to both the firstcoordinate and the first moving vector. The first displaying mediumincludes a micro dotmap displayed thereon. The first coordinateindicates a coordinate of a first encoding block on the displayed microdotmap. The second frame is retrieved by scanning the first displayingmedium at the second moment.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates scanning a displaying medium printed with a microdotmap by manipulating an optical scanning device in a hand-writingmanner so as to display tracks of the optical scanning device on ascreen corresponding to a movement of the optical scanning device on thedisplaying medium.

FIG. 2 illustrates a frame retrieved by scanning the displaying mediumshown in FIG. 1 with the optical scanning device shown in FIG. 1.

FIG. 3 schematically illustrates an embodiment of calculating a movingvector for calculating a coordinate in the present invention.

FIG. 4 illustrates a movement of the held optical scanning device shownin FIG. 1 between different moments.

FIG. 5 illustrates applying the method shown in FIG. 3 while the heldoptical scanning device shown in FIG. 1 moves and scans with a largerrange on the displaying medium.

FIG. 6 is a flowchart of the method of determining a coordinate on amicro dotmap by using a moving vector in the present invention.

FIG. 7 illustrates using a transparent or black displaying medium andwhite microdots on a liquid crystal display (LCD) for encoding microdotsin a similar manner with FIG. 1.

DETAILED DESCRIPTION

For relieving the delays caused by significant amounts of calculationsin decoding microdots in the prior art, the present invention disclosesa method of determining a coordinate on a micro dotmap with a movingvector for preventing completely and repeatedly recognizing allmicrodots in a data region, for significantly saving the significantamounts of calculations, and for reducing the delays.

Main characteristics in the disclosed method of the present inventionlie in using moving vectors for dynamically calculating according tomovements of the held optical scanning device 106 on the displayingmedium 104. Since calculating a moving vector is a technique ofcalculating a relative location, whenever the held optical scanningdevice 106 fetches frames on the displaying medium 104 at differentmoments, the plurality of microdots 128 of the data region 126 are notrequired to be repeatedly recognized to decode a current location of theframe 120. Instead, merely both a location, which is of scanning thedisplaying medium 104 by the optical scanning device 106 at a firstmoment, and a moving vector, which is generated according to differencesbetween frames at the first moment and a second moment, are required forcalculating a location of scanning the displaying medium 104 by theoptical scanning device 106 at the second moment. Moreover, a requiredamount of calculations are significantly reduced.

Please refer to FIG. 3, which schematically illustrates an embodiment ofcalculating a moving vector for calculating a coordinate in the presentinvention. In FIG. 3, a supposition, under which the user holds theoptical scanning device 106 shown in FIG. 1 to scan the frame 120 shownin FIG. 2 at a first moment t1, moves the optical scanning device 106rightward, and then scans a frame 140 at a second moment t2, is made.Note that for clearly describing a track for indicating a movement ofthe held optical scanning device 106, in FIG. 3, a frame center 210 isused for indicating a benchmark of scanning the frames 120 and 140 bythe optical scanning device 106, and a track indicating a movement ofthe frame center 210 between the first moment t1 and the second momentt2 is used for indicating the track indicating the movement of the heldoptical scanning device 106 between the first moment t1 and the secondmoment t2. However, note that the frame center 210 is merely a datastructure provided for enhancing the embodiment of the presentinvention. Therefore, for the user holding the optical scanning device106 to scan the displaying medium 104, the frame center 210 is notnecessarily perceivable or required. Note that for brevity of succeedingdescriptions, a coordinate of a micro dotmap printed on the displayingmedium 104 is regarded as a coordinate on the displaying medium 104.Moreover, as shown in FIG. 3, the frame 140 covers a plurality ofencoding blocks 122 located at coordinates (x+2, y), (x+3, y), (x+2,y+1), and (x+3, y+1).

Please refer to FIG. 4, which illustrates a movement of the held opticalscanning device 106 shown in FIG. 1 between different moments. In FIG.4, at the first moment t1, the held optical scanning device 106 scansthe displaying medium 104 so as to generate the frame 120. Then from thefirst moment t1 to the second moment t2, the held optical scanningdevice 106 is moved on the displaying medium 104 to generate the frame140.

The disclosed method of the present invention is described as follows,and please refer to both FIG. 3 and FIG. 4. Note that the disclosedmethod of the present invention is supposed to be implemented on abuilt-in arithmetic unit 401 included by the optical scanning device106. However, in other embodiments of the present invention, thedisclosed method is not limited to be implemented on the arithmetic unit401. At the first moment t1, when the held optical scanning device 106scans the frame 120 shown in FIG. 4, the built-in arithmetic unit 401 ofthe optical scanning device 106 recognizes an encoding block 122, atwhich the frame center 210 is currently located, according to locationsof different header regions 124 covered by the frame 120 in advance,i.e., the encoding block 122 occupying the coordinate (x, y) and shownin FIG. 3. Then the built-in arithmetic unit 401 of the optical scanningdevice 106 decodes the plurality of microdots 128 included by the dataregion 126 of the encoding block 122 occupying the coordinate (x, y) soas to calculate said coordinate (x, y).

Between the first moment t1 and the second moment t2, when the heldoptical scanning device 106 scans along the track of the frame center210 shown in FIG. 3 and FIG. 4 and retrieves the frame 140, the built-inarithmetic unit 401 of the optical scanning device 106 calculates acorresponding moving vector according to a movement of the frame center210 between the first moment t1 and the second moment t2, instead ofrecognizing a current coordinate (x+2, y) of the frame center 210 in theprior art. Methods of calculating the moving vector include (1)performing characteristic matching on both the frames 120 and 140, andcalculating the moving vector according to a result of thecharacteristic matching; (2) calculating a set of gray level differencesbetween a set of gray levels of the frame 120 and a set of gray levelsof the frame 140, and calculating the moving vector according to the setof gray level differences; and (3) calculating an optical flow betweenthe frames 120 and 140, and calculating the moving vector according tothe optical flow. The described methods for calculating the movingvector are known by those who skilled in the art so that said methodsare not further described for brevity.

After the arithmetic unit 401 perceives the coordinate (x, y) at thefirst moment t1 and the calculated moving vector between the moments t1and t2, the coordinate (x+2, y) of the encoding block 122, at which theframe center 210 is located at the second moment t2, may thus becalculated. With the aid of transmissions issued by the optical scanningdevice 106, the screen 102 displays the movement indicated by a track ofthe frame center 210 from the coordinate (x, y) to the coordinate (x+2,y). Compared to the prior art, it is beneficial of the disclosed methodof the present invention in preventing frequent recognitions anddecoding procedures related to each movement of the held opticalscanning device 106 on the displaying medium 104. Thereby, significantamounts of calculations are saved, and delays on the screen 102 causedby large amounts of calculations are also reduced.

Please refer to FIG. 5, which illustrates applying the method shown inFIG. 3 while the held optical scanning device 106 shown in FIG. 1 movesand scans with a larger range on the displaying medium 104. As shown inFIG. 5, while the held optical scanning device 106 moves and scans witha larger range on the displaying medium 104, by continuously calculatingmoving vectors, coordinates of the frame center 210 on the displayingmedium 104 may also be continuously simulated at different moments,where the directive track shown in FIG. 5 may be regarded as a setformed by a plurality of continuously calculated moving vectors.However, in practical movements of the held optical scanning device 106on the displaying medium 104, errors may be brought into coordinatesdetermined according to the calculated moving vectors because ofvibrations of the displaying medium 104. Besides, such errors may becontinuously accumulated while the optical scanning device 106 moves andscans with the larger range on the displaying medium 104 so that errorscorrespondingly occur in tracks of the frame center 210 on thedisplaying medium 104 and in movements of the frame center 210 shown onthe screen 102. for preventing the abovementioned errors from occurring,in one embodiment of the present invention, the optical scanning device106 decodes the data region 126 of the encoding block 122, at which theframe center 210 is located, with a variable interval or a constantperiod so as to determine an accurate and current coordinate of theframe center 210 and to thereby fix the abovementioned accumulatederrors. Therefore, errors between the track of the frame center 210 onthe displaying medium 104 and the practical movement of said framecenter 210 are eliminated as well. Note that the data region 126 may bedecoded at any time during the movements of the held optical scanningdevice 106, and it indicates that while the held optical scanning device106 is moved, a plurality of coordinates on the micro dotmap (or on thedisplaying medium 104) may be decoded between certain moments spacedwith variable intervals. Similarly, the data region 126 may also bedecoded with a fixed period (or a fixed interval) during movements ofthe held optical scanning device 106, ad it indicates that while theoptical scanning device 106 is moved, a plurality of coordinates on themicro dotmap (or the displaying medium 104) are decoded between certainmoments spaced with a fixed period or interval. Referring to theembodiment shown in FIG. 5, since there are accumulated errors in thetrack of the frame center 210, on the regions 122 shown in FIG. 5,locations of the frame center 210 are instantly corrected within theregions 122 with the aid of the abovementioned error-eliminatingtechniques in the present invention so as to prevent accumulations ofthe errors in the track of the frame center 210.

Please refer to FIG. 6, which is a flowchart of the method ofdetermining a coordinate on a micro dotmap by using a moving vector inthe present invention. As shown in FIG. 6, the method includes steps asfollows:

Step 602: Decode a first coordinate, which is located on a firstdisplaying medium displaying a micro dotmap and is of a frame center ofa first frame, where the first frame is retrieved by scanning the firstdisplaying medium at a first moment;

Step 604: Calculate a first moving vector according to both the firstframe and a second frame, which is corresponding to a current locationof the frame center at a second moment succeeding to the first moment,at the second moment, where the first moving vector is corresponding toa movement of the frame center between the first moment and the secondmoment;

Step 606: Determine a second coordinate of the frame center on the firstdisplaying medium according to both the first coordinate and the firstmoving vector at the second moment;

Step 608: Display a third frame on a second displaying medium accordingto both the first coordinate and the second coordinate; when the secondframe is required to be decoded for checking the second coordinate, goto Step 610; else, go to Step 604; and

Step 610: Check and update a current location of the frame center on thefirst displaying medium according to a result of decoding the secondframe.

Steps shown in FIG. 6 is a simplified summary of the disclosed method ofthe present invention. In Step 602, a coordinate of an encoding block122, at which the frame center 210 is currently located, is calculatedaccording to a frame 120 currently corresponding to the frame center 210on the displaying medium 104 at the first moment t1. In Step 604, amoving vector between the frames 120 and 140 is calculated according tocharacteristic differences between the frames 120 and 140 at the secondmoment t2 with the aid of the abovementioned techniques including thecharacteristic matching, gray level differences, and the optical flow,while the frame center 210 moves and the frame 140 is thereby retrieved.In Step 606, a coordinate of an encoding block 122, at which the framecenter 210 is located at the second moment t2, is calculated accordingto both the coordinate determined in Step 602 and the moving vectorcalculated in Step 604. In Step 608, a track corresponding to a movementof the frame center 210 between the first moment t1 and the secondmoment t2 is displayed on the screen 102 according to the coordinatecalculated in Step 606. For preventing the accumulated errors, atcertain moments, some coordinates calculated according to Step 606 haveto be checked in their accuracies, where the certain moments are spacedwith a fixed period or a variable interval. The check includes decodinga data region 126 of the encoding block 122, at which the frame center210 is located at the second moment t2, so as to check whether thecoordinated calculated in Step 606 is correct. When there are errors inthe coordinate calculated in Step 606, the coordinate of the framecenter 210 at the second moment t2 is instantly updated by a coordinatecalculated by decoding in Step 610. After the update is complete, Step604 is run again; and when the Step 606 is run again, the firstcoordinate used in Step 606 is just the coordinate used for updating asmentioned above. Besides, in Step 608, when the coordinate of the framecenter 210 is not required to be checked anymore, go to Step 604; aftera while when Step 606 is run again, the first coordinate used in Step606 is just the second coordinate calculated in a previous-adjacent runof Step 606. As shown in FIG. 6, an implicit recursive procedure relatedto Step 604, 606, 608, and 610 is continuously run along with movementsof the held optical scanning device 106. Even if the held opticalscanning device 106 stays at a same position for a while, the disclosedmethod of the present invention is still available.

In FIG. 1, the displaying medium 104 is colored in white to serve as abackground, and may be printed with black microdots for indicating boththe micro dotmap and the microdots illustrated in the above diagrams soas to implement the disclosed method of the present invention, where thedisplaying medium 104 may be implemented with an electronic displayingdevice or an electronic paper. However, the microdots may also beprinted with inks corresponding to various wavelengths in lights so asto match displaying media made of various materials or to match othertypes of microdot representations in other embodiments of the presentinvention. Please refer to FIG. 7, which illustrates using a transparentor black displaying medium and white microdots on a liquid crystaldisplay (LCD) for encoding microdots in a similar manner with FIG. 1. Ona conventional touch-triggered LCD, for preventing light reflection, adisplay panel of the LCD may be made of certain materials capable ofabsorbing visible lights. When the display panel is implemented with thedisclosed method of the present invention, as shown in FIG. 7, thedisplaying medium 104 may be implemented with transparent materials,such as a slide; paints or inks capable of reflecting lights may be usedfor printing microdots on the displaying medium 104; and the displayingmedium 104 may be attached to the screen 102 implemented with a LCD.Therefore, the disclosed method of the present invention may thus beapplied on the touch-triggered LCD. When the held optical scanningdevice 106 scans the displaying medium 104 attached to the screen 102,locations of microdots on the displaying medium 104 may be substantiallyperceived by detecting lights reflected by the microdots with the aid ofthe disclosed method of the present invention. Note that as long aswavelengths of visible lights or invisible lights absorbed by inks orpaints for printing the displaying medium and the microdots are notoverlapped with or close to each other so that the microdots can beclearly differentiated from the displaying medium while scanning thedisplaying medium, feasible replacements of both the microdots and thedisplaying medium or applications related to the feasible replacementsshould not be limited in embodiments of the present invention.Furthermore, replacing inks or paints printed on the microdots anddisplaying medium with materials capable of absorbing visible lights orinvisible lights of various wavelength domains are allowed inembodiments of the present invention as long as the abovementionedconditions related to respective wavelength domains are reached.

Note that the displaying medium 104 may be an electronic displayingdevice. The micro dotmap of the displaying medium 104 may be printed ona transparent plate with paints or inks. And the transparent plate maybe disposed above the electronic displaying device. Also, the microdotmap of the displaying medium 104 may be printed on the electronicdisplaying device.

The present invention discloses a method of determining a coordinate ona displaying medium printed with a micro dotmap by using a movingvector. With the aid of the disclosed method, when a held opticalscanning device moves and scans on the displaying medium, requiredcalculations for generating the moving vector are significantly fewer inthe present invention in comparison to the amount of calculationsbrought by frequently decoding the data region of each encoding block onthe micro dotmap in the prior art. Therefore, delays of the screendisplaying a frame are also significantly reduced while the opticalscanning device frequently moves and scans the displaying medium.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A method of determining a coordinate on a microdotmap according to a moving vector, comprising: decoding a firstcoordinate of a first frame corresponding to a first displaying mediumaccording to the first frame retrieved by scanning the first displayingmedium at a first moment, the first displaying medium including a microdotmap displayed thereon, and the first coordinate indicates acoordinate of a first encoding block on the displayed micro dotmap;scanning the first displaying medium at a second moment to retrieve asecond frame, wherein the second moment is later than the first moment;calculating a first moving vector according to at least one differencebetween the first frame and the second frame; and determining a secondcoordinate of the second frame corresponding to the first displayingmedium according to both the first coordinate and the first movingvector; wherein the first displaying medium is an electronic displayingdevice, the micro dotmap is printed on a transparent plate with paintsor inks, and the transparent plate is disposed above a displaying panelcomprised by the electronic displaying device.
 2. The method of claim 1wherein the second coordinate is a coordinate of a second encoding blocklocated on the micro dotmap.
 3. The method of claim 2 wherein each ofthe first encoding block and the second encoding block comprises aplurality of micro dots displayed with different permutations orcombinations.
 4. The method of claim 2 wherein each of the firstencoding block and the second encoding block is separated into a headerregion and a data region; the header region is used for recognizing anencoding block having said header region; and the data region is usedfor indicating a coordinate of an encoding block having said data regionon the first displaying medium.
 5. The method of claim 1 whereindecoding the first coordinate comprising: decoding the first coordinateaccording to the first encoding block on the first displaying medium, towhich a frame center of the first frame is corresponding at the firstmoment.
 6. The method of claim 1 wherein calculating the first movingvector according to the at least one difference between the first frameand the second frame comprising: calculating the first moving vectoraccording to a difference between a frame center of the first frame anda frame center of the second frame at the second moment.
 7. The methodof claim 1 further comprising: displaying a third frame on a seconddisplaying medium according to both the first coordinate and the secondcoordinate; wherein the third frame is corresponding to a movementbetween the first moment and the second moment while scanning the firstdisplaying medium.
 8. The method of claim 7 wherein the seconddisplaying medium is an electronic displaying device capable ofdisplaying the third frame according to the micro dotmap, the seconddisplaying medium displays a location of a frame center corresponding tothe second displaying medium on the third frame, and the frame center isof the first frame or the second frame on the first displaying medium.9. The method of claim 8 wherein both the first frame and the secondframe are retrieved by scanning the micro dotmap on the first displayingmedium with the aid of an optical scanning device, the optical scanningdevice comprises an arithmetic unit, which is capable of calculating thefirst moving vector according to both the first frame and the secondframe.
 10. The method of claim 8 wherein the second displaying mediumcomprises an arithmetic unit, which is capable of calculating the firstmoving vector according to both the first frame and the second frame.11. The method of claim 1 wherein the micro dotmap comprises a pluralityof encoding blocks, an plurality of micro dots on a header regioncomprised by each of the plurality of encoding blocks have a samecombination or a same permutation.
 12. The method of claim 1 wherein themicro dotmap comprises a plurality of encoding blocks, a permutation ora combination of a plurality of micro dots on a data region comprised byeach of the plurality of encoding blocks is implemented according to anencoding method and is used for indicating a coordinate of the encodingblock having the data region on the micro dotmap.
 13. The method ofclaim 1 further comprising: decoding a plurality of coordinatesaccording to a plurality of frames, which are retrieved by scanning thefirst displaying medium at a plurality of moments succeeding to thefirst moment; and checking and updating a location of a frame center ofeach of the plurality of frames on the first displaying medium at theplurality of moments according to the plurality of decoded coordinates.14. The method of claim 13 wherein the plurality of moments are spacedwith a constant period.
 15. The method of claim 13 wherein the pluralityof moments are spaced with a variable interval.
 16. The method of claim1 wherein the first displaying medium is a printable medium printed withthe micro dotmap.
 17. The method of claim 16 wherein both the firstframe and the second frame are retrieved by scanning the micro dotmap onthe first displaying medium with the aid of an optical scanning device.18. The method of claim 1 wherein calculating the first moving vectoraccording to the at least one difference between the first frame and thesecond frame comprises: calculating a set of gray level differencesbetween a first set of gray levels of the first frame and a second setof gray levels of the second frame; and calculating the first movingvector according to the calculated set of gray level differences. 19.The method of claim 1 wherein calculating the first moving vectoraccording to the at least one difference between the first frame and thesecond frame comprises: performing characteristic matching between thefirst frame and the second frame to generate a characteristic matchingresult; and calculating the first moving vector according to thegenerated characteristic matching result.
 20. The method of claim 1wherein calculating the first moving vector according to the at leastone difference between the first frame and the second frame comprises:calculating an optical flow between the first frame and the secondframe; and calculating the first moving vector according to thecalculated optical flow.
 21. The method of claim 1 further comprising:scanning the first displaying medium at a third moment succeeding to thesecond moment to retrieve a fourth frame; calculating a second movingvector on the first displaying medium and corresponding to a movementbetween frame centers of the second frame and the fourth frame; anddetermining a coordinate of the frame center of the fourth frame on thefirst displaying medium according to both the second coordinate and thesecond moving vector at the third moment.
 22. A method of determining acoordinate on a micro dotmap according to a moving vector, comprising:decoding a first coordinate of a first frame corresponding to a firstdisplaying medium according to the first frame retrieved by scanning thefirst displaying medium at a first moment, the first displaying mediumincluding a micro dotmap displayed thereon, and the first coordinateindicates a coordinate of a first encoding block on the displayed microdotmap; scanning the first displaying medium at a second moment toretrieve a second frame, wherein the second moment is later than thefirst moment; calculating a first moving vector according to at leastone difference between the first frame and the second frame; anddetermining a second coordinate of the second frame corresponding to thefirst displaying medium according to both the first coordinate and thefirst moving vector, without via decoding the second frame; wherein thefirst displaying medium is an electronic displaying device, the microdotmap is printed on a transparent plate with paints or inks, and thetransparent plate is disposed above a displaying panel comprised by theelectronic displaying device.
 23. A method of determining a coordinateon a micro dotmap according to a moving vector, comprising: decoding afirst coordinate of a first frame corresponding to a first displayingmedium according to the first frame retrieved by scanning the firstdisplaying medium at a first moment, the first displaying mediumincluding a micro dotmap displayed thereon, and the first coordinateindicates a coordinate of a first encoding block on the displayed microdotmap; scanning the first displaying medium at a second moment toretrieve a second frame, wherein the second moment is later than thefirst moment; calculating a first moving vector according to at leastone difference between the first frame and the second frame; anddetermining a second coordinate of the second frame corresponding to thefirst displaying medium according to both the first coordinate and thefirst moving vector; wherein the first displaying medium is anelectronic displaying device, the micro dotmap is printed on theelectronic displaying device.